<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Title</title>
<style type="text/css">
    .context-box {
        box-sizing: content-box;
        border: 1px solid red;
    }

    .border-box {
        box-sizing: border-box;
        border: 1px solid green;
    }
</style>
</head>
<body>
<div class="context-box">
    context-box
</div>
<div class="border-box">
    border-box
</div>
</body>
</html>